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Clinical manifestations and diagnosis of Rocky Mountain spotted fever

Authors
Daniel J Sexton, MD
Micah T McClain, MD
Section Editors
Stephen B Calderwood, MD
Sheldon L Kaplan, MD
Deputy Editor
Jennifer Mitty, MD, MPH

INTRODUCTION

Rocky Mountain spotted fever (RMSF) is a potentially lethal, but curable tick-borne disease, which was first described in Idaho in the 19th century. In 1906, Howard Ricketts demonstrated that RMSF was an infectious disease transmitted by ticks [1]. The clinical spectrum of human infection ranges from mild to fulminant disease [2].

The epidemiology, clinical manifestations, and diagnosis of RMSF will be reviewed here. The basic biology of Rickettsia rickettsii infection, the mechanisms of disease, and the treatment of this disorder are discussed separately. (See "Biology of Rickettsia rickettsii infection" and "Treatment of Rocky Mountain spotted fever".)

PATHOGENESIS

The etiologic agent, R. rickettsii, is a gram-negative, obligate intracellular bacterium with a tropism for vascular endothelial cells. Rickettsial infection leads to direct vascular injury; endothelial cells produce prostaglandins that may contribute to increased vascular permeability [3]. Activation of clotting factors ensues, but true disseminated intravascular coagulation rarely occurs. Hyponatremia results from release of antidiuretic hormone as an appropriate response to hypovolemia and reduced tissue perfusion [4]. The host response, which is secondary to vascular injury, can lead to a variety of clinical manifestations such as interstitial pneumonitis, myocarditis, and encephalitis.

MICROBIOLOGY

R. rickettsii does not grow in cell-free culture media. Growth of R. rickettsii requires living host cells (such as the yolk sac of embryonated eggs or cell culture). Gimenez or acridine orange stains are required for visualization of rickettsia on microscopy, since they do not take up routine Gram stain; rickettsiae are also small in size (ie, 0.3 by 1.0 micrometers). The cell wall contains peptidoglycan and lipopolysaccharide (LPS), similar to gram-negative bacteria.

Rickettsiae have surface proteins that are used for serotyping; these surface proteins (OmpA and OmpB) contain epitopes, which are the targets for humoral antibodies [5].

                            

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Literature review current through: Nov 2016. | This topic last updated: Wed May 18 00:00:00 GMT 2016.
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